Abstract
Variation in sperm traits is widely documented both at inter- and intraspecific level. However, sperm traits vary also between ejaculates of the same male, due for example, to fluctuations in female availability. Variability in the opportunities to mate can indeed have important consequences for sperm traits, as it determines how often sperm are used, and thus the rate at which they are produced and how long they are stored before the mating. While being stored within males’ bodies, sperm are subjected to ageing due to oxidative stress. Sperm storage may significantly impair sperm quality, but evidence linking male sperm storage and variation in sperm traits is still scarce. Here, we tested the effect of the duration of sperm storage on within-male variation in sperm traits in the zebrafish, Danio rerio. We found that without mating opportunities, sperm number increased as storage duration increased, indicating that sperm continue to be produced and accumulate over time within males without being discharged in another way. Long sperm storage (12 days) was associated with an overall impairment in sperm quality, namely sperm motility, sperm longevity, and sperm DNA fragmentation, indicating that sperm aged, and their quality declined during storage. Our results confirm that male sperm storage may generate substantial variation in sperm phenotype, a source of variation which is usually neglected but that should be accounted for in experimental protocols aiming to assay sperm traits or maximise fertilization success.
Highlights
Variation in sperm traits is widely documented both at inter- and intraspecific level
Sperm storage duration affected sperm number (p = 0.001), with sperm number increasing with the increase of duration of sperm storage (Fig. 2a)
We tested whether the duration of sperm storage within the male affected sperm production and quality in sperm of male zebrafish, by using a repeated measures design to account for intrinsic differences among males in sperm production and quality
Summary
Variation in sperm traits is widely documented both at inter- and intraspecific level. The huge variation observed in sperm traits across species has been widely documented and associated with different evolutionary trajectories determined by differences in ecology and mating systems. Such variation exists at the intraspecific level and has been reported in many taxa[1,2,3]. An example comes from the wild house mice (Mus musculus domesticus) in which males reared under high male density adaptively increase their sperm production[25] Another source of variability linked to social environment is female availability, and mating frequency. A meta-analysis showed that sexual rest of more than 5 days negatively affects a variety of sperm parameters, including sperm motility, viability and DNA integrity[36], which in turn impact clinical outcomes of assisted reproductive technologies[33]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
